After the big bang planet started to evolved. Then life emerged from randomness and due to carbon water combo or life came from extraterrestrial planet? Billions of years before Earth or our solar system were formed, space-journeying viruses and extraterrestrial microbes were deposited on planet after planet and continually exchanged DNA with species living on other worlds.

When we are going to talk about alien life, we have to presume some assumptions. Circumstantial evidence indicates alien civilisations are very few and far flung in the universe. I have pointed out that the easiest way to explore the universe is send out self-replicating space probes . Within a cosmologically short period of co-moving time (ie millions of years) we could colonise the Milky Way and the rest of the Local Group. The arrival of such a probe at a star system would preclude and supersede local biological evolution. Since life on Earth has evolved over billions of years then we can’t expect (statistically speaking) to find civilisations within our local group. Where are the aliens, asked Fermi. Many megaparsecs away!!

The critical question is:Is life the only type of material complexity expected in other habitable zones, or is life only one example of many types of complexity? In other words, is or is not life an inevitable consequence of the evolution of matter? Given the proper conditions and enough time, is life a sure bet or is it quite rare?

Maybe they merely want us as slaves? Or pets? Again, they could more easily and cheaply produce us at their own home planet for such purposes, than they could to come all the way here to capture us in large numbers fully grown, and then transport us back again.